Abstract: As recognized by the 2014 Nobel Prize in Chemistry to Dr. Hell, Dr Betzig and Dr. Moerner, there is a profound transformation occurring in the field of fluorescence nanoimaging. In a few years we went from what was thought to be impossible, that is to "see" molecules in living cells and tissues, to exploiting new concepts and building new type of microscopes in which the molecular world can be directly visualized and molecular interactions can be determined. Life is made of molecular interactions and molecular structures, many of them at the nanoscale, which were beyond our imaging capabilities until new discoveries and technologies were introduced to the field. Prof. Gratton will present the physical and engineering basis for the nanoimaging technology as well as some examples of visualizing structures and interactions at the nanoscale.